MATLAB: Need a method to arrange data

data arrangeMATLAB

How can i arrange a array a = [1 2 3 4 3 4 5 3 3 4 2 3 3 4 1 2 3 3 4];
here the numbers 1 ,2 ,…are the order or level in the hierarchy , 1 is top level. 2 is below 1 , 3 is below level 2 and so on.
from first occurence of 1 till next is 1 group of data .
Now i need to arrange array a into array b like this : b =[4 3 5 4 3 3 4 3 2 3 4 3 2 1 3 4 3 2 1];
here tree is like this for data from first 1 till next 1 in array a, i.e.: 1 2 3 4 3 4 5 3 3 4 2 3 3 4
1{
   2{
    3{
      4{
        } first 2 elements in array b are 4 ,3 from this part of tree.
      }
    3{
      4{
        5{
          } next 3 elements in b are 5 ,4, 3 ,and so on..
        }
      }
    3{
      }
    3{
      4{
        }
      }
     }
2{
  3{
    }
  3{
    4{
      }
    }
  }
}

Best Answer

I am sure there is a more efficient way to do this, but I cannot see it right off.
I = find(a==1);
b = [];
for ii = 1:length(I)
    if length(I)>=ii+1
          A = a(I(ii):I(ii+1));
      else
          A = [a(I(ii):end) 1];
      end
      B = [];
      D = [1 diff(A)];
      cnt = 1;
      while any(D<=0)
          L = find(D<=0,1,'first');
          L2 = L;
          X = A(L);
          Y = X+1;
          while Y>X
              Y = A(L-1);
              B(cnt) = Y;
              cnt = cnt + 1;
              L = L-1;
          end
          A(L:L2-1) = [];
          D = [1 diff(A)];
      end
      b = [b B];
  end
  b
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